A doctor's surgery in Coventry is under investigation for prescribing a 75 per cent increase of an addictive drug when the city health authority was aiming to reduce its use.

A doctor's surgery in Coventry is under investigation for prescribing a 75 per cent increase of an addictive drug when the city health authority was aiming to reduce its use.

The surgery, which has not been named but is in the north of the city, is giving out well above the recommended levels of the tranquilliser benzodiazepine.

Health chiefs are examining why the figures are so high in light of the fact that about 20 surgeries in the north of Coventry were last year asked to make efforts to reduce prescriptions of the sleeping tablet by five per cent.

Most of the practices decreased the use of the drug or remained at the same level as last year.

Pharmaceutical adviser David Maxted said: "There has been an overall drive to reduce the amount of benzodiazepine in Coventry.

"This 75 per cent increase at one practice appears to be an anomaly and will be checked by our clinical governance team."

Dr Ken Holton, who sits on the north Primary Care Group board, added: "Benzodiazepine includes Valium and is notorious for addiction.

"We wanted to cut its usage for it is addictive and because we discovered there is a black market for it in Coventry.

"The amount used in the city is certainly less than it was five years ago, but a 75 per cent increase on this occasion does seem significant."

He added that there could be a legitimate reason for the dramatic soar in prescribing the drug," he said.

"The north of Coventry has a lot of asylum seek-ers and perhaps it is appropriate to give them tranquillisers.

"Or maybe this particular practice is working with drug addicts and it may be appropriate to feed their habit."

Most benzodiazepines have a strong sedative effect and are said to relieve insomnia and anxiety.